Is this a case of boost spike?

[Lee Thompson]

Have a friend with an unopened 87----mods. include THDP (with stock type wastegate), bleeder valve, adjustable reg, 42 lbs. inj and a cold air kit. He had a 49 turbo and running 25 psi (steady) @ 12.12 and 114 mph. We changed out the 49 (It went bad) to a used John Craig 62. Now the boost goes to 25-26 in first but falls to 18 as soon as it shifts to second and stays there all through 3. I have 0 experience with a stock type wastegate. What is happening here? BTW, the puck does not have a great seal as the 62 is used and the sealing area is somewhat pitted. Is this a classic case of boost spike? I am wondering if we have the boost set @ 18 and it is spiking. Kinda afraid to raise the setting any as it might go higher in first.
Need advise from you experts!!!! Thanks

 

[John Larkin]

Sounds like boost spike but exaggerated. Mine used to spike about 3 psi. That was with no bleeder valve; rod tension and stock wastegate solenoid/stock Y fitting only. I assume his has bleeder valve, adjustable rod and a tuner-style looped vacuum hose. If this is true, it sounds like the bleeder valve is working but once engine load comes up it is blowing the puck open farther as load increases (more air is flowing). Therefore yes, I'd say it is set at 18. I am thinking the wastegate hole is probably too small for the puck causing the spike. If pressure blew on the puck steadily, it should open a set amount and remain there. I'd check puck coverage and see if the wastegate hole needs to be ported larger to the traditional 1/8" - 1/16" overlap. I'm sure you know the trick: grease the puck, reinstall pipe, close wastegate, remove pipe and look at the grease ring around the wastegate hole.

Opinion from a non-expert FYI.